Printing platen

ABSTRACT

A printing platen comprising a relatively soft elastomeric body and a thin sheet of relatively hard plastic or metal which is held taut against the surface of the body by spring pressure at the point where printing is to occur.

[ Nov. 4, 1975 United States Patent 1191 Roggensack [5 PRINTING PLATEN 1,801,396 4/1931 Thatcher.................... [75] Inventor: Richard L. Roggensack, El Monte, l963856 6/1934 A2123 Calif.

[73] Assignee: Addmaster Corporation, San

Gabnel Cahf' Primary Examiner-J. Reed Fisher Assistant Examiner-Edward M. Coven Attorney, Agent, or FirmFred N. Schwend [22] Filed:

Apr. 18, 1974 [21] Appl. No.: 461,997

l0l/93.41; 101/407 BP; lOl/287;

ABSTRACT A printing platen comprising a relatively soft elastomeric body and a thin sheet of relatively hard plastic or metal which is held taut against the surface of the body by spring pressure at the point where printing is to occur.

. 7 5 48 77 15 mm wa I 9 7 M 1%71. m M? 0 9 mfl 3. m sA M927 m m% .13P m ,B "m0 .8 5 m m 6 W 2h B C lol dw S M U 'mF l. .1] 2 00 5 55 [56] References Cited UNITED STATES PATENTS 3 Claims, 4 Drawing Figures US. Patent Nov. 4, 1975 PRINTING PLATEN BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the printing art and has particular reference to printing platens for transferring an imprint from a line of type characters onto a paper or like record medium.

2. Description of the Prior Art Heretofore, printing platens for gang printers have been formed of elastomeric material, such as rubber,

the material being soft enough to yield somewhat dur-- ing the printing impression so that an even imprint can be obtained across the entire line of print even though minute inaccuracies might exist in the height of certain of the type characters due to manufacturing tolerances, etc.

Although such prior art printing platens are generally satisfactory, they tend to produce relatively wide and fuzzy character lines and also tend to smudge or form an undesirable background imprint of the printing ribbon, particularly between ajdacent type characters and over the interstices between the character lands of a single type character.

Attempts have been made to overcome the above defects by bonding a thin hard shell of plastic or the like in intimate contact with an underlying body of soft elastomeric material. For example, in the US. Pat. No. 1,80l,396 to L. A. Thatcher a printing combination is disclosed comprising a thin walled shell of thermoplastic material which is secured over a relatively soft rubber body. The shell is nominally of a smaller inside diameter than the diameter of the body. It is first softened and then stretched to a larger diameter, and thereafter allowed to shrink into intimate contact with the body. Such construction is relatively costly and does not lend itself to mass production. Further, in the event of aging or wear of the shell due to extensive impacting by the type characters, it is difficult to replace the shell and would generally require replacement of the entire platen combination. In'addition, any stretching of the plastic shell due to impact by the type characters or the like will cause the shell to break away from the rubber body.

STATEMENT OF THE INVENTION A principal object of the present invention is to improve the quality of print in printers of the above noted Another object is to overcome the aforementioned defects of prior printing platens.

ent temperature changes.

Also, the stifi'ener. sheet may be readily replaced without having to likewise replace or even dismantle the platen body.

BRIEF DESCRIPTION OF THE DRAWINGS The manner in which the above and other objects of the invention are accomplished will be readily understood on reference to the following specification when read in conjunction with the accompanying drawing, wherein:

FIG. 1, is a sectional elevational view of a printer embodying a preferred form of the present invention.

FIG. 2, is a transverse sectional view of the printer and is taken along the line 22 of FIG. 1.

FIG. 3, is an enlarged fragmentary view illustrating the printing action of prior art platens.

FIG. 4, is viewed similar to FIG. 3 but illustrating the printing action of a printing platen constructed in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention is disclosed as embodied in the printer of the well known Addmaster electronic printing calculator. However, it should be understood that the invention may be equally well embodied in other types of printers.

Referring to the drawing, the printer disclosed therein comprises a plurality of plastic printing sectors 11 arranged in side-by-side relation and pivotally mounted independently on each other on a rockable support shaft 12. The latter is rotatably supported in bearings 13 carried by spaced printer side frames 14 and 15.

Each sector 11 has a somewhat flexible arcuate type section 16 which is integrally connected to the main body of the sector 11 by flexible end portions 17 and 18. Printing type characters 20 ranging in value from 0" to 9 are spaced along the length of each type section 16.

Means are provided to yieldably advance the various type sectors 11 clockwise from their illustrated home positions until differentially arrested in positions presenting selected type characters to a printing station 21. After a printing impression, as will be described later, the sectors 11 are returned counterclockwise to their home positions.

For the purpose of moving the sectors 1 1, a cyclically operable drive shaft 22 is suitably driven clockwise one revolution for each cycle of the printer. An arm 23 carried by shaft 22 is pivotally connected at 24 to a link 25 which, in turn, is connected at 26 to an arm 27 attached to the shaft 12.

Arms 28 and 30 are fastened to the shaft 12 and carry the ends of a bail rod 31 which extends through openings 32 in the sectors 11 and frictionally engages depressions 33 formed in yieldable tails 34 formed integrally with the sectors 1 1. As the drive shaft 22 and arm 23 move through the first half of a revolution, link 25 and arm 27 will rock the shaft 12 and thus carry the bail 33 through approximately to yieldably drive the various sectors 11 accordingly.

Means provided to selectively arrest the different type sectors 11 so as to present selected type characters 20 at the printing station 21. For this purpose, a stop pawl 35 is provided for each sector. The pawls 35 are independently pivoted on a rod 36 and are adapted to engage any of a plurality of spaced stop teeth 37 formed on the sector. The pawls 35 are moved into blocking relation with the stop teeth 37 by electromag netic coils 38. Each coil surrounds one leg of a U- 3 shaped magnet core 40. Upon energization of a coil 38, an iron armature 41, pivoted at 42, is attracted upwardly and in doing so forces a rod 43 to rock the associated pawl 35 into blocking engagement with whichever sector tooth 37 is next adjacent the pawl at the time the latter is actuated.

A paper tape 44 is guided through a guide channel 45 and extends between an inked ribbon 46 and a platen 47. The tape 44 is deflected upwardly by a concave surface formed on a tear-off member 48. Suitable line spacing means, not shown, is provided to push the paper 44 endwise through the channel 45 and on past the platen 47 as an incident to each printing operation.

A combined aligning and back-up bar 50 extends through the openings 32 in the sectors 11 and is guided for vertical movement in guide slots 51 formed in the side frames 14 and 15.

Cam formations 52 are formed on the cam levers 28 and 30 and are arranged to engage the rod 50 after the various sectors 11 have been differentially arrested by the stop pawls 35 to cam the rod 50 upwardly into centering engagement with detent notches 53 formed in the type section 16 so as to accurately align the type characters at the printing station 21.

The printing platen 47 comprises a platen body 54 of relatively soft rubber or other elastomeric material, preferably having a hardness on the order of 30 to 35, as measured on a Shore durometer (A scale). The body 54 is mounted on a platen shaft 55 which is guided at its ends for vertical movement in slots 56 formed in the side frames 14 and 15. Links 57 are connected between the shaft 55 and a pivot rod 58 connected to a toggle bail 60 which, in turn, is pivotally supported on a rod 61 extending between the side frames 14 and 15.

A cam 62 on drive shaft 22 is engageable with a cam follower 63 pivotally supported at 64 and connected by a link 65 to the pivot rod 58. During a printing operation and while the detent rod 50 is in engagement with the type section 16, the cam 62 actuates the toggle linkage to lower the platen 47 until it engages the tape 44 to transfer an imprint from the line of type characters 20 at the printing station, through the inked ribbon 46 and onto the paper tape.

According to the present invention, a sheet 66 of thin, hard thermoplastic material, such as is known in the art as MYLAR, on the order of 0.010 inches thick, is wrapped around the platen body 54, and is held taut in intimate contact with the lower surface of the body by a pair of tension springs 67 extending between the ends of the sheet 66 and the pivot bar 58. It has been found that a metal stiffener sheet on the order of 0.008 to 0.010 inch thick may be used in lieu of a plastic sheet. In either case, such stiffener sheet has the characteristic that it strongly resists compound bending, that is, concurrent bending about intersecting axes and thus resists deformation into the interstices between adjacent type character lands 67, FIG. 4, forming the type characters 20. Accordingly, the arc a, FIG. 4, representing the area of direct contact between the ribbon 46 and the tips of the character lands 67 is relatively small and therefore a clear, crisp character line will be transmitted to the paper 44. On the other hand, the stiffener sheet 66 and platen body 54 will readily accomodate any minor differences in height of the character lands 67 on a single type sector 16 due to manufacturing tolerances or other inaccuracies in manufacturing, so that an even print will be applied along the print line.

The above is in contrast to prior art platens, as exemplified in FIG. 3, wherein a harder elastomeric platen 68, generally of a Shore hardness of from 70 to 90 (A scale), is used to directly transfer an imprint from the type characters through an inked ribbon 46a to a paper tape 44a. Here, as the platen 68 is impressed against the paper tape it tends to deform, as shown at 70, into the space between adjacent character lands 67a, resulting in a relatively large arc b of direct contact between the ribbon 46a and the tips of the character lands 67a, thereby transferring a relatively wide character line to the paper tape. Further, due to such deformation of the platen and paper between adjacent character lands, the paper and ribbon 46a are stretched, tending to transfer an undesirable background imprint between the ribbon and the paper along the print line.

I claim:

1. In a data printer,

means carrying printing type characters,

a printing platen extending over said type characters and normally spaced therefrom,

means for causing said platen and said type characters to impress a record medium therebetween,

said platen comprising a body of relatively soft elastomeric material,

a stiffener sheet of relatively hard flexible material extending over said body, and

means including a spring acting on said stiffener sheet for maintaining said stiffener sheet taut in intimate contact with a portion of said platen body against which said record medium is impressed.

2. In a data printer,

a plurality of type members arranged in side-by-side relation and carrying type characters,

a printing platen extending over said type characters and normally spaced therefrom, and

means for causirig said platen and said type characters to impress a record medium therebetween,

said platen comprising a cylindrical body of relatively soft elastomeric material,

a stiffener sheet of relatively hard flexible material wrapped over the portion of said body which lies adjacent said type characters, and

means including a spring acting on said stiffener sheet for maintaining said sheet inv intimate contact with said portion of said body.

3. In a data printer, a plurality of type members arranged in side-by-side relation and carrying type characters,

a printing platen extending over said type characters and normally spaced therefrom,

a toggle device comprising first and second link members;

said first link member being connected at one end to said platen,

a pivot member connecting said first link member at the opposite end thereof to one end of said'second link member, and

means pivotally supporting the opposite end of said second link member;

means for actuating said toggle device to cause said platen to impress a record medium against said type characters,

said platen comprising a body of relatively soft elastomeric material,

a stiffener sheet of relatively hard flexible material wrapped around said platen body, and

spring means extending between said stiffener sheet ener sheet in intimate contact with said platen.

and said pivot member for maintaining said stiff- 

1. In a data printer, means carrying printing type characters, a printing platen extending over said type characters and normally spaced therefrom, means for causing said platen and said type characters to impress a record medium therebetween, said platen comprising a body of relatively soft elastomeric material, a stiffener sheet of relatively hard flexible material extending over said body, and means including a spring acting on said stiffener sheet for maintaining said stiffener sheet taut in intimate contact with a portion of said platen body against which said record medium is impressed.
 2. In a data printer, a plurality of type members arranged in side-by-side relation and carrying type characters, a printing platen extending over said type characters and normally spaced therefrom, and means for causing said platen and said type characters to impress a record medium therebetween, said platen comprising a cylindrical body of relatively soft elastomeric material, a stiffener sheet of relatively hard flexible material wrapped over the portion of said body which lies adjacent said type characters, and means including a spring acting on said stiffener sheet for maintaining said sheet in intimate contact with said portion of said body.
 3. In a data printer, a plurality of type members arranged in side-by-side relation and carrying type characters, a printing platen extending over said type characters and normally spaced therefrom, a toggle device comprising first and second link members; said first link member being connected at one end to said platen, a pivot member connecting said first link member at the opposite end thereof to one end of said second link member, and means pivotally supporting the opposite end of said second link member; means for actuating said toggle device to cause said platen to impress a record medium against said type characters, said platen comprising a body of relatively soft elastomeric material, a stiffener sheet of relatively hard flexible material wrapped around said platen body, and spring means extending between said stiffener sheet and said pivot member for maintaining said stiffener sheet in intimate contact with said platen. 